The present invention relates to a flap for air ducts and to a flow guide device, such as is generally known.
In air ducts, flaps are used to switch multi-conduit flow lines located downstream of the flap. The flaps may in this case serve, on the one hand, for a continuous variable distribution of the air streams between the downstream conduits or else also for a complete alternating changeover of the fluid path of the air stream between the various conduits.
Thus, correspondingly designed flaps have sealing devices which, in cooperation with throughflow orifices present on the flow guide devices, can provide leaktight bearing contact, so that conduits can be closed off in a fluidtight manner.
Such flaps for controlling the ducts take up a specific construction length in the throughflow direction of the air. This construction length is determined essentially by the dimensions of the flap and by the construction space required for adjusting the flap into various positions. Furthermore, the construction space required in this case depends on how large a design the flap has. The larger the design of the flap, the longer is the pivoting space required for the flap. However, the situation is that large flap sizes have the advantage that the cross section of coverable throughflow orifices increases with the flap size. The reason for designing air lines with as large duct cross sections as possible is that, for the same volumetric flow, a lower flow velocity of the air stream is then required. This allows a better provision of laminar airflows which cause substantially few flow noises than turbulent flows. Where flow guide devices are concerned, it is fundamentally necessary to avoid the generation of flow noise, since this is transferred, together with the emerging air stream, into the ventilated space.
On the other hand, it is also troublesome when large construction spaces are taken up for switching devices. Large construction spaces and free flow lengths making it possible to arrange a flap of large size are not always available in the regions where switchable flow routing is to be provided.
This problem arises particularly in the field of vehicle ventilation and air conditioning devices. There are often only small construction spaces available in vehicles. The devices which are used for the ventilation and air conditioning of a vehicle are to have as small a build and as compact a design as possible. In this context, in air conditioning systems in vehicles, it is customary first to route the entering air stream as a whole via an evaporator which cools down and dehumidifies the air stream. An initial state of the inflowing air stream to be defined as simply as possible for the air conditioning of the vehicle interior is generated. The evaporator is then followed, in the flow path of the air stream, by a bypass line which leads past a heating body, and, parallel to this bypass line lies the flow path or the conduit leading through the heating body. By means of switchable flaps, the air coming from the evaporator and conditioned in terms of temperature and humidity is divided into part streams which are distributed to the two conduits. Downstream of the heating body and, if appropriate, of other devices, the two conduits are combined again, and the two part streams are intermixed. The temperature and air humidity of the mixed stream occurring are conditioned by the position of the flaps dividing the air stream into part streams. Thus, by means of the flap position, the division of the ratio of the two part streams in relation to one another is varied. Precisely where arrangements of this type are concerned, the construction space required between the evaporator and the heating body must be kept as small as possible. Within this construction space, it must be possible to arrange the flap and for the latter to perform its function as a control element for dividing into part air streams.